<!doctype html>
<html>
    <head><title>Test-title</title></head>
    <script>
        window.name = 'test-main-frame'
        onload = (e) => {
            const frames = window.frames;
            for (let i = 0; i < frames.length; i++) {
                frames[i].name = 'test-subframe' + i;
            }
        };
    </script>
    <frameset cols="50%, 50%">
        <frameset cols="50%, 50%">
            <frame style="border: red dashed 1em;"/>
            <frame style="border: green dashed 1em;"/>
        </frameset>
        <frame style="border: blue solid 1em;"/>
    </frameset>
</html>
